Electronic equipment is supplied by single and multiphase A.C. currents in both Y and Delta configurations. The performance of this equipment under these various supply currents is critical especially when interrupted and restored.
Inrush currents produced by transformers can destroy components of the electronic equipment and also trip circuit breakers. Values of inrush current are generally determined by the switching of units under test OFF and ON a number of times while observing the inrush current waveform with an oscilloscope. This technique does not assure that the worst-case condition has been obtained; consequently, the test does not produce the sufficiently precise data needed for the power distribution system design. Also, many electronic equipments such as computers and the like are designed to continue normal operation when subjected to momentary power disturbances. This capability is normally provided by furnishing critical units with backup power.
The inventor has discovered that if he could interrupt the voltage at precise phase angles and again restore the voltage at precise known phase angles, he could obtain the maximum inrush current. Moreover, he could study the response of the electronic equipment to power outages and accordingly design protection circuits or backup equipment which would prevent any untoward events such as the destruction of components and the loss of data. Knowing precisely when and how the equipment should respond to various phase angles of interrupts and restorations, the inventor can also test existing equipment in order to evaluate precisely the equipment compliance with specifications.
The inventor, therefore, has discovered a method and designed the equipment to carry out that method which permits him to interrupt power to the electronic equipment at selected sample phase angles spaced over an entire cycle. Furthermore, he can restore power to the electronic equipment at selected sample phase angles over many cycles. The entire operating limits of interruption and restoration needing to be studied and sampled to determine the compliance of preexisting equipment with known or stated specifications is now possible with the availability of the present invention.